Kotlin Specialist

What it does

When your agent uses it

• Writing coroutine and Flow code with correct cancellation
• Sharing code across platforms with Kotlin Multiplatform
• Building Android screens with Jetpack Compose and ViewModel
• Setting up a Ktor server with routing, authentication and serialization
• Designing a type-safe DSL with builders and scope functions

Example prompts

• “Refactor this repository class to use structured concurrency instead of GlobalScope.”
• “Model the loading, success and error states of the profile screen with a sealed class.”
• “Set up a Kotlin Multiplatform module for shared networking code with expect and actual declarations.”
• “Add a Ktor route group with authentication and JSON serialization for the orders API.”

Requirements

• `detekt` and `ktlint` for the validate step

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Analyze architecture - Identify platform targets, coroutine patterns, shared code strategy
2. 2Design models - Create sealed classes, data classes, type hierarchies
3. 3Implement - Write idiomatic Kotlin with coroutines, Flow, extension functions
4. 4Validate - Run detekt and ktlint; verify coroutine cancellation handling and null safety
5. 5Optimize - Apply inline classes, sequence operations, compilation strategies
6. 6Test - Write multiplatform tests with coroutine test support (runTest, Turbine)

What it can do on your machine

Read from SKILL.md and the folder at commit 1be15d8. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are kotlin).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • github.com
  • synergetic.solutions
  • jeffallan.github.io

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Kotlin Specialist loads about 1.5k tokens when it runs, and up to ~13k if it reads all its reference files. Until then it costs about 116 tokens; SKILL.md has 360 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~116

When it runs · the whole SKILL.md, loaded when a task matches

~1.5k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~13k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Jeffallan/claude-skills at commit 1be15d8, republished under its MIT licence (© Jeffallan). 360 words, ~1,525 tokens.

name

kotlin-specialist

description

Provides idiomatic Kotlin implementation patterns including coroutine concurrency, Flow stream handling, multiplatform architecture, Compose UI construction, Ktor server setup, and type-safe DSL design. Use when building Kotlin applications requiring coroutines, multiplatform development, or Android with Compose. Invoke for Flow API, KMP projects, Ktor servers, DSL design, sealed classes, suspend function, Android Kotlin, Kotlin Multiplatform.

license

MIT

metadata.author

https://github.com/Jeffallan

metadata.company

https://synergetic.solutions

metadata.version

1.1.0

metadata.domain

language

metadata.triggers

Kotlin, coroutines, Kotlin Multiplatform, KMP, Jetpack Compose, Ktor, Flow, Android Kotlin, suspend function

metadata.role

specialist

metadata.scope

implementation

metadata.output-format

code

metadata.related-skills

test-master

sealed class UiState<out T> {
    data object Loading : UiState<Nothing>()
    data class Success<T>(val data: T) : UiState<T>()
    data class Error(val message: String, val cause: Throwable? = null) : UiState<Nothing>()
}

// Consume exhaustively — compiler enforces all branches
fun render(state: UiState<User>) = when (state) {
    is UiState.Loading  -> showSpinner()
    is UiState.Success  -> showUser(state.data)
    is UiState.Error    -> showError(state.message)
}

// Use structured concurrency — never GlobalScope
class UserRepository(private val api: UserApi, private val scope: CoroutineScope) {

    fun userUpdates(id: String): Flow<UiState<User>> = flow {
        emit(UiState.Loading)
        try {
            emit(UiState.Success(api.fetchUser(id)))
        } catch (e: IOException) {
            emit(UiState.Error("Network error", e))
        }
    }.flowOn(Dispatchers.IO)

    private val _user = MutableStateFlow<UiState<User>>(UiState.Loading)
    val user: StateFlow<UiState<User>> = _user.asStateFlow()
}

// Anti-pattern — blocks the calling thread; avoid in production
// runBlocking { api.fetchUser(id) }

// Prefer safe calls and elvis operator
val displayName = user?.profile?.name ?: "Anonymous"

// Use let to scope nullable operations
user?.email?.let { email -> sendNotification(email) }

// !! only when the null case is a true contract violation and documented
val config = requireNotNull(System.getenv("APP_CONFIG")) { "APP_CONFIG must be set" }

// apply — configure an object, returns receiver
val request = HttpRequest().apply {
    url = "https://api.example.com/users"
    headers["Authorization"] = "Bearer $token"
}

// let — transform nullable / introduce a local scope
val length = name?.let { it.trim().length } ?: 0

// also — side-effects without changing the chain
val user = createUser(form).also { logger.info("Created user ${it.id}") }

© Jeffallan, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (references) in skills/kotlin-specialist of Jeffallan/claude-skills.

• SKILL.md
• references/android-compose.md
• references/coroutines-flow.md
• references/dsl-idioms.md
• references/ktor-server.md
• references/multiplatform-kmp.md

Open the folder on GitHubat commit 1be15d8